Re: [kvm-unit-tests PATCH v2 2/7] s390x: Consolidate sclp read info

[Thomas Huth <thuth@redhat.com>]

On 27/11/2020 14.06, Janosch Frank wrote:
> Let's only read the information once and pass a pointer to it instead
> of calling sclp multiple times.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> ---
>  lib/s390x/io.c   |  1 +
>  lib/s390x/sclp.c | 29 +++++++++++++++++++++++------
>  lib/s390x/sclp.h |  3 +++
>  lib/s390x/smp.c  | 28 +++++++++++-----------------
>  4 files changed, 38 insertions(+), 23 deletions(-)
> 
> diff --git a/lib/s390x/io.c b/lib/s390x/io.c
> index c0f0bf7..e19a1f3 100644
> --- a/lib/s390x/io.c
> +++ b/lib/s390x/io.c
> @@ -36,6 +36,7 @@ void setup(void)
>  {
>  	setup_args_progname(ipl_args);
>  	setup_facilities();
> +	sclp_read_info();
>  	sclp_console_setup();
>  	sclp_memory_setup();
>  	smp_setup();
> diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
> index 4e2ac18..ff56c44 100644
> --- a/lib/s390x/sclp.c
> +++ b/lib/s390x/sclp.c
> @@ -25,6 +25,8 @@ extern unsigned long stacktop;
>  static uint64_t storage_increment_size;
>  static uint64_t max_ram_size;
>  static uint64_t ram_size;
> +char _read_info[PAGE_SIZE] __attribute__((__aligned__(4096)));
> +static ReadInfo *read_info;
>  
>  char _sccb[PAGE_SIZE] __attribute__((__aligned__(4096)));
>  static volatile bool sclp_busy;
> @@ -110,6 +112,22 @@ static void sclp_read_scp_info(ReadInfo *ri, int length)
>  	report_abort("READ_SCP_INFO failed");
>  }
>  
> +void sclp_read_info(void)
> +{
> +	sclp_read_scp_info((void *)_read_info, SCCB_SIZE);
> +	read_info = (ReadInfo *)_read_info;
> +}
> +
> +int sclp_get_cpu_num(void)
> +{
> +	return read_info->entries_cpu;
> +}
> +
> +CPUEntry *sclp_get_cpu_entries(void)
> +{
> +	return (void *)read_info + read_info->offset_cpu;
> +}
> +
>  /* Perform service call. Return 0 on success, non-zero otherwise. */
>  int sclp_service_call(unsigned int command, void *sccb)
>  {
> @@ -127,23 +145,22 @@ int sclp_service_call(unsigned int command, void *sccb)
>  
>  void sclp_memory_setup(void)
>  {
> -	ReadInfo *ri = (void *)_sccb;
>  	uint64_t rnmax, rnsize;
>  	int cc;
>  
> -	sclp_read_scp_info(ri, SCCB_SIZE);
> +	assert(read_info);
>  
>  	/* calculate the storage increment size */
> -	rnsize = ri->rnsize;
> +	rnsize = read_info->rnsize;
>  	if (!rnsize) {
> -		rnsize = ri->rnsize2;
> +		rnsize = read_info->rnsize2;
>  	}
>  	storage_increment_size = rnsize << 20;
>  
>  	/* calculate the maximum memory size */
> -	rnmax = ri->rnmax;
> +	rnmax = read_info->rnmax;
>  	if (!rnmax) {
> -		rnmax = ri->rnmax2;
> +		rnmax = read_info->rnmax2;
>  	}
>  	max_ram_size = rnmax * storage_increment_size;
>  
> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
> index 675f07e..6620531 100644
> --- a/lib/s390x/sclp.h
> +++ b/lib/s390x/sclp.h
> @@ -271,6 +271,9 @@ void sclp_wait_busy(void);
>  void sclp_mark_busy(void);
>  void sclp_console_setup(void);
>  void sclp_print(const char *str);
> +void sclp_read_info(void);
> +int sclp_get_cpu_num(void);
> +CPUEntry *sclp_get_cpu_entries(void);
>  int sclp_service_call(unsigned int command, void *sccb);
>  void sclp_memory_setup(void);
>  uint64_t get_ram_size(void);
> diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c
> index 77d80ca..f77ad1e 100644
> --- a/lib/s390x/smp.c
> +++ b/lib/s390x/smp.c
> @@ -25,7 +25,6 @@
>  #include "smp.h"
>  #include "sclp.h"
>  
> -static char cpu_info_buffer[PAGE_SIZE] __attribute__((__aligned__(4096)));
>  static struct cpu *cpus;
>  static struct cpu *cpu0;
>  static struct spinlock lock;
> @@ -34,8 +33,7 @@ extern void smp_cpu_setup_state(void);
>  
>  int smp_query_num_cpus(void)
>  {
> -	struct ReadCpuInfo *info = (void *)cpu_info_buffer;
> -	return info->nr_configured;
> +	return sclp_get_cpu_num();
>  }
>  
>  struct cpu *smp_cpu_from_addr(uint16_t addr)
> @@ -228,10 +226,10 @@ void smp_teardown(void)
>  {
>  	int i = 0;
>  	uint16_t this_cpu = stap();
> -	struct ReadCpuInfo *info = (void *)cpu_info_buffer;
> +	int num = smp_query_num_cpus();
>  
>  	spin_lock(&lock);
> -	for (; i < info->nr_configured; i++) {
> +	for (; i < num; i++) {
>  		if (cpus[i].active &&
>  		    cpus[i].addr != this_cpu) {
>  			sigp_retry(cpus[i].addr, SIGP_STOP, 0, NULL);
> @@ -245,22 +243,18 @@ extern uint64_t *stackptr;
>  void smp_setup(void)
>  {
>  	int i = 0;
> +	int num = smp_query_num_cpus();
>  	unsigned short cpu0_addr = stap();
> -	struct ReadCpuInfo *info = (void *)cpu_info_buffer;
> +	struct CPUEntry *entry = sclp_get_cpu_entries();
>  
> -	spin_lock(&lock);

You've removed the spin_lock(), but not the spin_unlock() at the end of the
function ... looks wrong to me? I guess you rather should keep the
spin_lock() call here?

> -	sclp_mark_busy();
> -	info->h.length = PAGE_SIZE;
> -	sclp_service_call(SCLP_READ_CPU_INFO, cpu_info_buffer);
> +	if (num > 1)
> +		printf("SMP: Initializing, found %d cpus\n", num);
>  
> -	if (smp_query_num_cpus() > 1)
> -		printf("SMP: Initializing, found %d cpus\n", info->nr_configured);
> -
> -	cpus = calloc(info->nr_configured, sizeof(cpus));
> -	for (i = 0; i < info->nr_configured; i++) {
> -		cpus[i].addr = info->entries[i].address;
> +	cpus = calloc(num, sizeof(cpus));
> +	for (i = 0; i < num; i++) {
> +		cpus[i].addr = entry[i].address;
>  		cpus[i].active = false;
> -		if (info->entries[i].address == cpu0_addr) {
> +		if (entry[i].address == cpu0_addr) {
>  			cpu0 = &cpus[i];
>  			cpu0->stack = stackptr;
>  			cpu0->lowcore = (void *)0;
> 

Apart from the spin_lock() problem, patch looks fine to me now.

 Thomas